There seems to be an issue with both the recapthcha and the image upload facilities with wordpress 3.5
I'm not sure what the issue is with recaptcha not sending te correct words but with the images there seems to be an issue with mime types.
I can upload an image but the plugin says that the image is not an image type. If I check my media library the image has been uploaded but is not attached to the lisitng.
Resource interpreted as Image but transferred with MIME type text/html
I've checked my headers and my htaccess files and there is no problems there.